A new study appears to validate reports from women who experience changes to their menstrual cycles after receiving COVID vaccinations, but researchers are saying not to panic. Per the New York Times, some women experienced later periods than usual, while others said bleeding became heavier or was accompanied by pain. Researchers at Oregon Health & Science University and the Warren Alpert Medical School of Brown University examined the records of almost 4,000 women who tracked their menstrual cycles using a birth control app called Natural Cycles. Of the women, 2,400 of them were vaccinated.
Per the AP, the study found that, on average, the next period after a shot started about a day later than usual. The study found no change in the number of days of menstrual bleeding after COVID-19 vaccination. “This is incredibly reassuring,” said Dr. Alison Edelman, who led the research and said it's important to tell women what to expect. The unvaccinated women saw no significant changes. So why the difference? Edelman said one theory is that when the immune system revs up at certain times in the cycle, “our body clock or what controls the menstrual cycle can have a hiccup.” She plans additional study to tell if there are changes in the heaviness of menstrual bleeding or if women who have irregular periods react differently. (Read more coronavirus vaccine stories.)